Domestic clothes dryers are a common household appliance that, in conjunction with domestic washers, have reduced the burden of laundry of many households by reducing the amount of time devoted by household caregivers to washing and drying clothes. Such clothes dryers typically include a housing (also known as a bulkhead) and a rotating drum, cylinder, supported within the housing. Commercially available air vented domestic clothes dryers use the rotating drum to tumble loads of washed clothes in a heated environment by generally using a blower/fan to pull ambient air across heater coils to raise the temperature of air passing into the drum. The heated air is pulled through the tumbling clothes and out through a lint screen for discharge. Commercially available condensing domestic clothes dryers also use the rotating cylinder to tumble loads of laundry in a heat environment, but treat the air in a slightly different manner. These condensing domestic clothes dryers use a blower/fan to pull ambient air across heater coils into the drum, through the tumbling clothes and out through a lint screen, across a condenser coil to remove moisture, and then return to the drum.
The dryers have doors used to access the interior of the drum of the respective dryers and these door use door seals to provide a tight seal of the door around the bulkhead and the drum. These door seals help to maintain a constant pressure and temperature within the drum of the dryer during operation.
Despite their widespread use in U.S. homes, clothes dryers are involved in a significant number of residential fires. According to some estimates, dryer fires produce annual U.S. property losses approaching $100 million, and lead to multiple consumer deaths and hundreds of injuries. Proper installation and effective maintenance of clothes dryers can significantly reduce the risk of appliance-related fires. But recent research has shown that product construction and design considerations are also important elements in building safer dryers.
The causes of electric dryer fires have been extensively researched over the past decade by the U.S. Consumer Product Safety Commission (CPSC), industry associations including the Association of Home Appliance Manufacturers (AHAM), individual appliance manufacturers, and standards organizations including Underwriters Laboratories (UL). Some research has pointed to the accumulation of lint and the subsequent reduction of air flow as a primary cause of dryer fires. Yet, other testing has supported claims that the cause of dryer fires can be attributed to a number of factors. In particular, studies have found that factors such as a dryer load, a dryer's electrical system, and a dryer's mechanical system also played a major role in reported dryer fires.
While increased consumer education regarding risks with dryer use can help reduce the number of dryer fires, attention can be focused on the design of dryers themselves, and the ability of a dryer unit to actually contain a fire, should one occur. United States (U.S.) fire regulations have been defined by UL Appliance Containment # UL 2158, which requires that a fire in the appliance be contained within the appliance and not allowed to escape into the environment surrounding the appliance. For fires that initiate inside the drum, one potential point of egress is the mating area between the cylinder and the front door and/or rear bulkhead. Clothes dryer fires have a wide temperature range depending on the fuel value of the load plus any fuel value items in the unit construction such as plastic baffles, friction reducing rings, fittings or bulkhead components, etc. The temperatures have been tested to exceed 1300° F. and cycle between low and high values. These temperatures exceed the capability of sustaining structural integrity of traditionally used wool and polyester nonwoven materials, even FR treated polyesters.
Another serious and dangerous situation that arises when a fire starts or begins to smolder within the drum is the opportunity of a smoke explosion. A smoke explosion is a condition whereby the rapid increase in pressure inside the drum/combustion chamber during a dryer fire is sufficient to overcome the door lock mechanism. The lock specification has been tested and indicated a twelve (12) foot pounds locking force. Therefore, these smoke explosions provide a great release of force that can create opportunity for bodily injury to people in the vicinity of the dryer and can cause the fire to spread quickly from being contained in the dryer to areas surrounding the dryer and to other parts of the house. These smoke explosions occur when a fire is contained in the drum producing smoke and providing a spark. Tests have shown that, as fire burns, the mixture of carbon monoxide (CO) from the white smoke, which contains residual unburnt hydrocarbons, and oxygen (O2) can occur within drum. The fire ignites this deadly mixture once it is achieved to explosive and horrific effect. Such a condition is known as pyrolysis.
To help control and reduce such combustion events within the drum of the dryer, efforts have mainly been concentrated on the containment features of the drum seals and wiring tracks from the control console and electrical components. Thereby, much of the research work in containing and reducing these combustion events has been focused upon these items.
The interior of the clothes dryer drum within a dryer is accessed through a door which is fitted with a deformable/crimp type seal. The dryer and its door are produced in either side hinge or drop down hinge styles. The door seal for the dryer door is normally configured in 2 (two) basic formats: a specialist circular knitted wire substrate with an aramid woven or knitted sleeve fitted over the substrate; or a PVC Extruded ‘D’-section molding with additional fin structure to broaden the crimp envelope. The D-section molding is much cheaper to produce and is provided at a lower cost than the knitted wire substrate. While the knitted wire substrate provides better sealing and protection during a fire or combustion event, it has been found that neither door seal operates very well in containing and/or reducing such fire or combustion events.
As such, a need exists for improved dryer door seals that an help reduce the opportunity of combustion events and smoke explosions within dryers and that can help contain fires that initiate inside of a drum of a clothes dryer.